High frequency induction system



Dec. 5, 1944. c, w. HANSELL HIGH FREQUENCY INDUCTION SYSTEM Filed July10, 1941 2 Sheets-Sheet 2 Patented Dec. 5, 1944 UNITED STATES PATENTOFFICE Clarence W. Hansell, Port Jefl'erson, N. Y., assignor to RadioCorporation of America, a corporation of Delaware Application July 10,1941, Serial No. 401,171

13 Claims.

This invention relates to a new and useful high frequency inductionsystem and particularly to a system which forms a section of a highfrequency concentric line.

An object of this invention is to simplify and improve high frequencyinduction systems generally.

Another object of this invention is to produce standing waves along amovable inner conductor of a high frequency concentric line which willbe independent of the movement and rate of speed of the inner conductor.

Still another object of this invention is to provide a means of limitingthe length of a fixed or movable conductor, forming a part of theinduction system, to any desired portion of the conductor withoutrequiring any physical connection at the ends of the limited portion.

A further object of this invention is to apply heat to the innerconductor for practical industrial applications, one of which will beexplained in more detail throughout the specification.

A feature of this invention is the novel arrangement of a section of aconcentric line having a movable conductor which is electricallyterminated by high impedance means.

Briefly, by means of my improved induction system, high frequencycurrents are made to flow in the'irmer conductor which may be movable orfixed, the current fiow being accomplished by means of electro-magneticcoupling through the air. The movable inner conductor is arranged withinan outer conductor forming a section of a concentric line simulating atransmission line I in such a way that it will not be necessary to makeany physical or direct electrical connection to the inner conductor. Thelength of the portion of inner conductor contained within the outerconductor is tuned to a high frequency current in such a way that itwill carry standing waves of potential and current. These waves willcause power to be dissipated in the movable inner conductor which is notuniform but which has a distribution along the wire which approximates asine squared curve. When there is a continuous movement of the conductorin the direction of its length, then, because of its heat retentivity,the temperature rise will be less variable along the wire than thevariation in power distribution. However, the faster the movement of thewire, the more uniformity of temperature will be obtained.

This invention will best be understood by referring to the accompanyingdrawings, in which:

Fig. 1 shows the physical arrangement of the electrical system of thisinvention;

- Fig. 2 shows a longitudinal sectional view of a practical industrialapplication of this invention;

Fig. 3 shows a cross-section of Fig. 2 taken on the plane 33;

Fig. 4 is a detail of an air pressure means used in conjunction with thearrangement shown in Figs. 2 and 3;

Fig. 5 is another detail of an air pressure means as applied to thearrangement shown in Figs. 2 and 3; and

Fig. 6 is a detail of an adjustable nozzle used with the air pressuremeans shown in Figs. 4 and 5.

Fig. 1 shows an arrangement in which a movable conductor 1 is placedwithin a stationary cylindrical conductor 6, the two conductors forminga section of a concentric line simulating a transmission line. Theinner, movable conductor or wire l is centrally arranged within tube 6by means of pulleys 3' and by tension in the wire. At each end of outerconductor 6 an electrical filter l and 1 is provided. This filter is inthe form of a disc having an aperture 8 therein, to which is soldered arelatively short metallic tube 5 which concentrically surrounds movableconductor I. The electrical length of tube 9 is such as to be tuned toquarter-wave resonance at the frequency at which the main portion of theline is resonant and at which standing electrical waves are set up.Adjacent to the filters l and 1' are arranged a pair of filters Ill andill. The filters l0 and ID are similar in construction to filters l andl and are likewise each tuned to a quarter-wave resonance. At someconvenient point along the conductors, movable conductor l iselectro-magnetically coupled to loop conductor H, which is connected toa source of high frequency power l2. In practice, I prefer to couple toone of the inner quarter-wave filter sec: tions, such as section l0, asshown. The filter section readily transfers the power to the remainderof the inner line section. It is to be understood that coupling toconductor 1 may be made at any position within the section of theconcentric line, except near a point of maximum potential and minimumcurrent. Instead of the inductive coupling loop H, I may employ acapacitive coupling, applied at any point except near a point of minimumpotential and maximum current.

It will be seen that,"with a given line section formed of a wire I andpipe 6 which may be about fifty feet (approximately fifteen. meters)long, if it is tuned to the frequency of the source l2, it will carrystanding waves of potential and current. These waves will cause power tobe dissipated in conductor I, which is not uniform but which has adistribution along the conductor. Because of the continuous movement ofthe wire and its heat retentivity, the temperature rise will be muchless variable along the wire than the variation in power distribution.Naturally, the faster the wire moves, the more uniform will be itstemperature. The power dissipated in conductor I will appear in the formof heat on the outer surface for the reason that, due to the quiredheating current and therefore the potenwell-known skin eflect," veryhigh frequency current will flow only on the surface of conduc tor I.Since the effective resistance of the conductor to the flow of highfrequency current is very much greater than the resistance to the flowof low frequency current, less current will be required at highfrequencies for a given power dissipation. To prevent loss of power'andelectromagnetic radiation from conductor I, filters 'I, I, I and III areprovided to offer ahigh impedance at points l4, i4, i5 and I5.

It will be seen that with such an arrangement, high frequency currentsare set up in a controllable manner ina length of movable wire, such aswould be subject to a heating process, without making any physicalconnection with the wire.

tial gradient would be reduced in inverse proportion to the square rootof the resistivity. Iron wire, or strip steel, due to its magneticproperties and very great skin effect, as well as 'high resistivity,would require relatively low current and potential gradients.

Figs. 4, 5 and 6 show several arrangements for automatic pneumaticcontrol of the thickness Furthermore, this is done without allowingapvice 24, the leads of which pass through insulators and 28. At thelower portion of the tube of this 593-;

' therefore the diameter of the finished wire, be-

of the enamel by air pressure, the simplest form of which is disclosedin Fig. 4, wherein a movable wire or strip 2| passes first through theautomatically adjusted die or wiper 43, then through the drying chamber42 (which is similar to Fig. 2) then through a split sleeve 4| which isarranged to be a loose fit' around the finished wire. The

. air leak between wire 2| and sleeve 4|, and therefore the. pressureapplied to the pressure motor control and relay 41, is governed by thefinished wire diameter. If the thickness of enamel, and

comes too great, the pressure rises and reduces the effective diameterof the motor controlled 22 is arranged an enamel tank-21 through whichthe wire to be enameled passes. Interposed between the enamel tankandfilter I an adjustable die or wiper 28 is arrangedso' as to governthe enamel thickness. It is preferable that the wiper be automaticallyadjusted to give the diameter desired for the finished wire. At theupper portion of tube 22, an air-sealdevice 28 is arranged to preventescape of the solvent and entrance to the surrounding air. In order thatthe surplus solvent and its vapors may not build up dangerous pressures,a vent 30 is provided disturb the enamel. Also, because the heat -isdeveloped at the inside surface of the enamel, the drying will tend tobe from the inside out;

ing chamber 42 affect the finished wire diameter.

consequently, it will be possible to apply heavier enamel coats or todry a given thickness of enamel more quickly than if the heat came fromthe outside, as is the method of enameling wire which is known in theprior art. Furthermore, since only the wire, itself, is heated, not anenveloping oven structure, as in the prior art, the power required foroperating my enamel drying system is much less than it is in the, priorsystems.

By the improved process of this invention,

there is lesstendency for formation of a tight outer skin whichcan-blister fromevaporating solvent trappedunder it during rapid'drying.Instead, each'infinitesimal layer as it hardens or dries is shrunk onthe layers underneath it which are alreadyhardand dry. g

If higher resistance non-magnetic wire other than that of copper is tobe enameled, the rewiper 43. Likewise, if the finished wire diameter'istoo small, the pressure falls and through the relay .4! andthe motorincreases the effective diameter of the wiper 43. Air compressed incompressor 44 passes through an automatic pressure regulator 45 toneedle valve 46 and thence into the connection between relay 4'! and theWith this arrangement,

split sleeve air leak II. the exact diameter of the finished wire iscontrollable over a considerable range by adjustvalue of the finishedwire diameter to keep it I To a certain de-g.

within allowable tolerances. gree, the speed of the wire and the amountof high frequency electrical power fed into the dry- The'refore, wirespeed, power input, the setting of needle valve 46, the enamelcomposition, original wire and enamel temperatures and other factors areall coordinated to obtain a desired result.

Fig. 5 shows in more detail, a further arrangement of controlling theenamel thickness by means of compressed air, in which the movable wire2| passes upward through a chamber II from the enamel tank 21, thencethrough the drying chamber 22 and then up through an air chamber 52which is connected to a valve 53 which controls the pressure fordetermining the finished outside diameter of the enamel. Connected fromthe compressed air input tank 44, a pressure regulating device 54 isarranged to be in fluid communication with valve 53 and member 5i. Thepressure in member 54 is regulated by means of a valve handle 55 whichprovides an adjustable spring pressure upon a movable diaphragm on whichis mounted valve or regulating member 55, which regulates the pressureentering an aperture 51. The air fiow through r' members 5| and 52 isregulated by a suitable amplifying air flow regulator 51'.

In operation of the device, air leaking in through adjustable needlevalve 53 builds up a pressure on the upper side of the diaphragm ofamplifying air flow regulator 51', the. amount of which is dependentupon the finished wire diameter, and therefore the rate of air leakagethrough member 52. This pressure regulates the pressure taken up by thewire and by this means holds the finished wire diameter substantiallyconstant at a value adjusted by needle valve 53.

Fig. 6 shows in detail an arrangement wherein an adjustable nozzle 6| isarranged to control the thickness of the enamel on the movable wire 2|by means of an air blast, wherein wire 2| passes through an aperture 62in a threaded spindle 63, the air entering the adjustable nozzle at apoint 64. This arrangement. as well as others, may be used for element5| of Fig. 5.

The advantages of this system over that of the prior art methods ofenameling wire is that high frequency'currents can be set up in thewires in a practical manner without making any physical or directelectrical connection to them. Low frequency currents cannot be usedbecause the enamel prevents physical connection if it is desired to havea continuous enameling process. Another advantage of this invention isthat by applying heat from the inside, the enamel layer dries fasterthan can be accomplished by prior art methods and without the danger ofblistering due to the formation of an outer enamel skin having a solventtrapped beneath it. Also, by drying the wire from the inside out, it ispossible for the enamelto be applied in fewer coats, or even in a singlecoat, instead of five or six coats, as previously employed. The methodgreatly reduces the amount of wire bending in the enameling process andalso reduces factory space to process the wire. Likewise, by means ofthis invention, the manufacturing operations will be speeded and thusthe production output of enamel wire will be increased.

While only one major industrial application of this system is shown, itis to be distinctly understood that this system may be used for otherapplications, such as raising and controlling the temperature of wire orstrip to be annealed or tempered in a continuous process as described inmy Patent #2,128,776. It may be employed not alone for drying enamelcontaining a solvent, but also may be used for applying materials inliquid or aste form which harden when heated and cooled withoutevaporating a solvent. It may be employed to apply glazed enamelscontinuously to metal wire, rods or tube by drying or decomposing avehicle liquid or paste and fusing together ground glazing particles. Itmay be used to apply metal coatings to other materials, as for example,applying platinum or gold by reduction of a solution of the chloride ofthe metal. It may be used for continuous case hardening of moving wireor strip either by rapid heating and cooling of an outer layer, or byheating in an atmosphere which changes the chemical composition of thesurface layer. Also, the system of this invention may be applied to forman antenna transmission line having a moving conductor.

What is claimed is:

1. Apparatus for providing an elongated, electrical conductor with acoating, said apparatus comprising, in combination, a tube ofelectrically conductive material forming the outer conductor of aconcentric line, said tube being provided with resonant filter elementsat each end through which said conductor passes without directelectrical contact therewith, a source of high frequency power forsetting up electrical currents in said conductor, means for drawing saidconductor through said tube, means for applying a coating on saidconductor before it passes through said tube, and automatic, pneumaticmeans responsive to the dimensions of the finished conductor as itleaves said tube associated with said conductor at a point between saidcoatm8 applying means and said tube for controlling the thickness ofcoating adherin to said conductor before it enters said tube.

2. Apparatus for providing an elongated wire conductor with an insulatedcoating, said apparatus comprising, in combination, a tank containing aliquid insulating material capable of becoming hard when heated to asuitable temperature, a relatively short, electrically conductive tube,means for moving said wire first through said tank whereby to applythereto a coating of said material and then longitudinally through saidtube in concentric relation therewith, said tube and said wirecooperating Jointly as a concentric transmission line of which said tubeacts as an outer conductor and said wire as an inner conductor, meansfor applying to said line a high frequency current of suihcientmagnitude to heat the portion of said wire instantaneously within saidtube to said temperature whereby to effect hardening of the insulatingmaterial coating around said portion, and pneumatic means associatedwith said wire and automatically operable in. response to the thicknessof said hard coating to control the thickness of coating on said wireprior to entry of succeeding portions thereof into said tube.

3. Apparatus for producing heating current in a movable conductor whichcomprises, in combination, a hollow, electrically conductive member offinite length adapted to act as one element of a conductive linesimulating a transmission line and along which said movable conductor isadapted to be moved in spaced relation thereto, said movable conductorconstituting a second element of said lin in association with saidconductive member, means associated with said line for coupling saidline to a source of alternating electrical energy, and impedance meansconnected to said member and associated with said movable conductor forconfining the current produced in said line by said coupling means to apredetermined portion of said line.

4. Apparatus for producing heating current in a movable conductor whichcomprises, in combination, a hollow, electrically conductive member offinite length adapted to act as one element of a conductive linesimulating a transmission line and along which said movable conductor isadapted to be moved in spaced relation thereto, said movable conductorconstituting a second element of said line in association with saidconductive member, means coupled to said line at a point intermediatethe ends thereof for coupling said line to a source of high frequencyenergy, and impedance means connected to said member in proximity to theends thereof in association with said movable conductor for confiningthe high frequency current produced in said line to substantially thatportion thereof which lies between said impedance means.

5. Apparatus, according to claim 4 characterized in that said means forcoupling said line to said source comprises a reactive element.

6. Apparatus according to claim 4 characterized in that said means forcoupling said line to said source comprises an inductive element.

7. Apparatus according to claim 4 characterized in that said means forcoupling said line to said source comprises an inductive element, andcharacterized further in that said inductive ele- 4 ment is inductivelycoupled to said line at one of said impedance means.

8; Apparatus according to claim 4 characterized in that said hollowmember is constituted by a tubular conductor, and characterized furtherin that said movable conductor is constituted by a wire of greaterlength than said tubular conductor, said wire being arranged for passageconcentrically through said tubular conductor whereby to form therewitha concentric line.

9. Apparatus for inducing heating current in a movable conductor whichcomprises, in combination, electrically conductive means providing astationary chamber through which said conduotor is adapted to be movedand in association with which said conductor constitutes one element ofa conductive line simulating atransmission line, means'associated withsaid line at a point intermediateits ends for inductively coupling saidline to a source of high frequency energy to thereby induce a highfrequency current in. that portion of said conductor which isinstantaneously within said chamber, and impedanee means at each end ofsaid chamber associated with said conductor for confining said highfrequency current to substantially that portion of said conductor whichlies instantaneously between said impedance means.

10. Apparatus according to claim 9 characterized in that said chamberproviding means comprises a tubular conductor of finite length,characterized further in that said movable conductor comprises a wire ofmuch greater length, said wire being arranged concentrically with saidtubular conductor in its passage therethrough whereby to provide aconcentric line, and characterized still further in that the length ofsaid line is so related to the frequency of said source that standingwaves are set up along a predetermined portion of said line between saidimpedance means.

11. Apparatus according to claim 9 characterized in that said chamberproviding means comprises a tubular conductor of finite length,characterized further in that said movable conductor comprises a wire ofmuch greater length, said I tion.

' wire being arranged concentrically with saidtubular conductor in itspassage therethrough whereby to provide a concentric line, said linebeing tuned to resonance at the frequency of said source, andcharacterized further in that said impedance means comprises means timedelectrically to quarter wave length resonance at said frequency.

12. In apparatus for providing an elongated conductive member with acoating of insulating material, the combination of means for advancingsaid member along a predetermined path, means at one point in said pathfor applying to said member a coating of insulating material which isadapted to become set upon being heated to a suitable temperature, meansat a succeeding point in said path for heating said coating to effectsetting thereof, and automatic, pneumatic means associated with saidmember and responsive to the dimension of the set coating forcontrolling the thickness of the coating applied to said member at saidfirst named point.

13. In apparatus for providing an elongated r mediate said first andsecond named stations and also at a fourth stationbeyond said secondstation in the direction of movement of said memher, the pneumatic meansat said fourth station being responsive to the dimensions of the setcoating for automatically rendering the pneu-.

matic means at said third station eflective to control the thickness ofthe coating adhering to said member as it leaves said third named sta-CLARENCE w. nansm.

